1. Field of the Invention
The present invention relates to an optical transmission module including an optical device, an optical fiber, and a holding member in which the optical fiber is inserted, and an endoscope with the optical transmission module.
2. Description of the Related Art
In endoscopes, an image pickup section including an image pickup device, such as a CCD, is provided in a distal end portion of an elongated insertion section. In recent years, use of image pickup devices with a high pixel count in endoscopes has been studied. When an image pickup device with a high pixel count is used, a signal amount transmitted from the image pickup device to a signal processing apparatus increases. Thus, optical signal transmission via an optical fiber using optical signals is preferably employed instead of electrical signal transmission via a metal wire using electrical signals. In the optical signal transmission, an E/O module (electrical-optical converter) that converts electrical signals to optical signals, and an O/E module (optical-electrical converter) that converts optical signals to electrical signals are used.
For example, Japanese Patent Application Laid-Open Publication No. 2013-025092 discloses an optical transmission module including an optical device where an optical signal is inputted or outputted, a board on which the optical device is mounted, and a holding section that has a through hole into which an optical fiber is inserted for transmitting the optical signal inputted and outputted to and from the optical device, and is mounted and arranged to be aligned with the optical device in a thickness direction.
In the optical transmission module, it is necessary to perform accurate positioning of relative positions of the optical device and the holding section (ferrule) where the optical fiber is inserted. That is, when a center position of a light emitting section of the optical device and a center position of the through hole of the holding section are out of alignment, a light intensity or the like entering the optical fiber decreases, and the signal is attenuated.
Here, to reduce a burden on a subject and ensure an observation field of view, an outer diameter and a length of the distal end portion of the insertion section of the endoscope are preferably reduced as much as possible. Therefore, the optical transmission module for endoscopes is much smaller than an optical transmission module for normal communications. Consequently, particularly accurate positioning is required between the optical device and the optical fiber.